EXCHANGE 


BOBl'lZWlVd 

'A  'N  '; 


UNIVERSITY  OF  PENNSYLVANIA 

I.  A  Separation  of  Arsenic,  Antimony 

and  Vanadium  from  Tungsten 

II.  On  the  Complex  Bismuthico  tung- 

states 


A  THESIS  PRESENTED  TO  THE  FACULTY  OF  THE  GRADU- 
ATE SCHOOL  IN  PARTIAL  FULFILMENT  OF  THE 
REQUIREMENTS  FOR  THE  DEGREE  OF 
DOCTOR  OF  PHILOSOPHY 


BY 

ORLAND  RUSSELL  SWEENEY 


EASTON.  PA.: 

ESCHENBACH  PRINTING  COMPANY 
1916 


UNIVERSITY  OF  PENNSYLVANIA 

I.  A  Separation  of  Arsenic,  Antimony 

and  Vanadium  from  Tungsten 

II.  On  the  Complex  Bismuthico  tung- 

states 


A  THESIS  PRESENTED  TO  THE  FACULTY  OF  THE  GRADU- 
ATE SCHOOL  IN  PARTIAL  FULFILMENT  OF  THE 
REQUIREMENTS  FOR  THE  DEGREE  OF 
DOCTOR  OF  PHILOSOPHY 


BY 

ORLAND  RUSSELL  SWEENEY 


EASTON.  PA.: 

ESCHENBACH  PRINTING  COMPANY 
1916 


ACKNOWLEDGMENT. 

The  author  wishes  to  express  his  sincere  thanks  to  Dr. 
Edgar  F.  Smith  under  whose  direction  and  personal  en- 
couragement this  study  was  undertaken. 


I.     A   SEPARATION    OF    ARSENIC,    ANTIMONY 
AND  VANADIUM  FROM  TUNGSTEN. 

INTRODUCTION. 

A  great  number  of  separations  of  various  elements 
have  been  effected,  in  this  laboratory,  by  passing  various 
gases,  or  vapors,  over  the  heated  samples.1 

Smith  and  Oberholtzer2  found  that  tungsten  was  not 
volatile  in  hydrogen  chloride,  and  because  of  this  fact  it 
was  thought  that  a  separation  of  this  metal  from  some  of 
those  elements  which  are  volatile  in  hydrogen  chloride 
might  be  satisfactorily  effected. 

In  his  study  of  the  complex  inorganic  acids  Gibbs3 
pointed  out  that  there  were  no  good  methods  for  the 
analysis  of  those  bodies  containing  tungsten  and  the  vari- 
ous other  elements  which  he  introduced.  The  investi- 
gators cited  above  found  that  many  of  those  elements 
were  volatile  in  hydrogen  chloride. 

With  these  thoughts  in  mind  a  study  of  the  separation 
of  arsenic,  antimony  and  vanadium  from  tungsten  was  be- 
gun; and  methods  have  been  developed  which,  it  is  be- 
lieved, will  satisfactorily  effect  their  separation  and  esti- 
mation. 

PREPARATION    OF   MATERIAL. 

All  reagents  used  in  this  work  were  carefully  purified. 
Nitric  acid  was  prepared  by  mixing  a  good  grade  of  the 
commercial    product    with    sodium    hydrogen    phosphate 


1  Smith  and  Hibbs:     Jour.  Amer.   Chem.  Soc.,   16,  578.     Smith 
and  Hibbs:     Zeit.  f.  anorg.  Chem.,  7,    41.     Smith    and  Oberholtzer: 
Jour.  Amer.  Chem.  Soc.,  15,  i.     Smith    and  Maas:     Zeit.    f.  anorg. 
Chem.,  5,  280;  Jour.  Amer.  Chem.  Soc.,  17,  682.      Smith  and  Meyer: 
Jour.  Amer.  Chem.  Soc.,  17,  735.     Moyer:     Jour.  Amer.  Chem.  Soc., 
18,   1029.     Keeley  and  Smith:     Jour.  Amer.   Chem.   Soc.,    18,    1096. 
Smith  and  Field:     Jour.  Amer.  Chem.  Soc.,  18,  1051  and  others. 

2  Zeit.  f.  anorg.  Chem.,  4,  236. 

3  Amer.  Chem.  Jour.,  2,  281. 

(3) 


444341 


and   distilling.     The  middle  portions  were  collected  sep- 
arately and  again  distilled. 

Hydrochloric  acid  was  prepared  pure  by  treating  the 
"C.  P."  acid  with  copper  wire  to  remove  traces  of  arsenic, 
after  which  the  hydrogen  chloride  was  expelled  from  its 
water  solution  with  sulphuric  acid;  the  gas  was  collected 
in  pure  redistilled  water. 

Tungsten  trioxide  was  prepared  from  crude  sodium 
tungstate  by  the  method  of  Smith  and  Kxner.1  After 
recrystallizing  the  crude  tungstate  twice  the  trioxide  was 
precipitated  with  nitric  acid,  and  was  boiled  in  the  mother 
liquor  until  it  settled  well.  It  was  then  washed  by  de.can- 
tation  until  it  began  to  settle  slowly,  after  which  it  was 
covered  with  water  and  ammonia  was  distilled  into  it 
until  nearly  everything  had  dissolved.  The  solution, 
after  decanting  from  the  excess  of  trioxide,  was  evaporated 
on  the  water-bath  and  allowed  to  crystallize.  The  crystals 
of  ammonium  tungstate  were  added  to  hot  nitric  acid,  and 
treated  with  hydrochloric  acid  as  recommended  by  the 
investigators  cited  above.  The  trioxide  obtained  in  this 
manner  was  again  dissolved  in  ammonia,  and  the  same 
procedure  repeated  three  times.  The  resulting  trioxide 
had  a  uniform  yellow  color,  and  portions  of  it  left  no  resi- 
due when  treated  with  two  per  cent  sodium  carbonate 
solutions.1 

Sodium  carbonate  was  purified  by  treating  the  "C.  P." 
product  with  a  few  grams  of  calcium  carbonate  and  fusing 
in  a  platinum  dish.  The  melt  was  dissolved  in  water, 
filtered,  and  carbon  dioxide  passed  in  until  the  sodium 
acid  carbonate  separated.  The  acid  carbonate  was  drained, 
centrifuged  and  ignited  to  the  normal  carbonate.  This 
was  dissolved  and  again  precipitated. 

Sodium  tungstate  was  prepared  by  mixing  the  purified 
trioxide  with  a  little  more  than  the  theoretical  amount 
of  sodium  carbonate,  fusing  in  platinum,  and  recrys- 

1  Proc.  Amer.  Phil.  Soc.,  43,  176. 


tallizing  the  product  twice.  Since  sodium  carbonate 
cannot  be  completely  removed  from  sodium  tungstate  by 
recrystallization,1  the  tungsten  content  was  determined 
by  analysis.  Potassium  tungstate  was  prepared  in  a  simi- 
lar manner. 

Sodium  pyroarsenate  was  prepared  by  recrystallizing 
a  good  grade  of  sodium  hydrogen  arsenate,  gently  igniting 
to  expel  the  water  of  crystallization,  and  finally  igniting, 
at  200°  C.  for  an  hour.  The  heating  should  be  very 
gentle'  at  first  or  the  arsenate  melts,  and  dissolves  in  its 
own  water  of  crystallization. 

Potassium  arseno-tungstate  was  prepared  by  the  Method 
of  Gibbs.2  Solutions  of  the  5  :  12  potassium  tungstate 
and  potassium  di-hydrogen  arsenate  were  mixed,  and  after 
evaporating  on  the  water-bath,  a  white  soluble  body 
separated.  It  was  filtered,  washed  and  dried  on  the  water- 
bath. 

Potassium  antimonio-tungstate  was  prepared  by  boiling 
a  solution  of  potassium  tungstate  with  an  excess  of  potas- 
sium hydrogen  pyro-antimonate  for  about  four  hours. 
The  suspended  matter  was  then  filtered  out  and  on  standing 
a  white  crystalline  precipitate  separated.  It  was  filtered, 
washed  with  cold  water,  and  dried  over  calcium  chloride. 

Vanadio-tungstic  acid  was  prepared  by  dissolving 
pure  sodium  tungstate  and  sodium  vanadate  in  water  and 
treating  with  an  excess  of  nitric  acid.  The  reddish  brown 
precipitate  which  resulted  was  washed  and  dried  on  the 
water-bath. 

SEPARATION    OF   ARSENIC   FROM   TUNGSTEN. 

The  plan  adopted  was  to  first  subject  weighed  portions 
of  the  arsenate  and  tungstate,  to  the  action  of  hydrogen 
chloride,  in  order  to  learn  whether,  or  not,  they  could 
be  separated  quantitatively.  Next  the  arseno-tungstate 


1  Taylor:     U.  of  P.  thesis,  1901. 

2  Amer.  Chem.  Jour.,  2,  290. 


was  treated  in  order  to  learn  whether,  or  not,  a  separation 
could  be  effected  when  they  were  combined  chemically. 

The  apparatus  used  is  shown  in  Fig.  i.  Hydrogen 
chloride,  generated  by  dropping  sulphuric  acid  into  hydro- 
chloric acid,  was  passed  through  two  wash-bottles  con- 
taining sulphuric  acid.  It  entered  the  combustion  tube 
at  A,  passed  over  the  sample  contained  in  the  tube  B, 


and  was  absorbed  in  the  flask  C.  The  tube  was  bent  at  a 
right  angle  at  D,  and  contained  the  bulbs  E,  E,  E,  which 
prevented  the  liquid  in  the  flask  from  being  drawn  back 
into  the  tube.  The  tube  rested  in  an  iron  trough  and 
was  heated  by  wing-top  burners.  Glass  joints  were  used 
throughout,  although  they  were  not  absolutely  necessary. 
In  order  to  test  the  apparatus  some  pure  sodium  pyro- 
arsenate  was  treated  with  the  dry  hydrogen  chloride. 
Almost  theoretical  results  were  obtained  for  the  residual 
sodium  chloride,  and  the  arsenic  was  found  to  be  all  ex- 
pelled. The  volatilized  arsenic  was  collected  in  water 
containing  nitric  acid.  The  resulting  solution,  after  boil- 
ing to  oxidize  the  arsenic,  was  made  ammoniacal,  and  the 
arsenic  precipitated  with  magnesia  mixture.  The  results 
were  invariably  low.  Careful  experiments  proved  that  no 
arsenic  escaped  absorption.  Various  modifications  were 


made  in  the  procedure,  but  the  method  was  finally  aban- 
doned. Others  who  have  studied  this  method  found  it 
very  unsatisfactory.1 

The  procedure  which  was  found  most  satisfactory  for 
the  estimation  of  the  arsenic  was  as  follows:  The  vol- 
atilized arsenic  was  absorbed  in  about  eight  hundred  cc. 
of  water.  After  rinsing  out  the  combustion  tube  the  solu- 
tion, in  the  receiver,  was  diluted  to  fourteen  hundred  cc. 
and  was  then  saturated  with  sulphur  dioxide.  After  stand- 
ing one  hour  the  solution  was  boiled,  while  a  stream  of 
carbon  dioxide  was  passed,  until  all  the  sulphur  dioxide 
was  removed.  Hydrogen  sulphide  was  then  passed  in 
until  precipitation  was  complete.  The  excess  of  hydrogen 
sulphide  was  then  removed  by  a  stream  of  carbon  dioxide, 
the  arsenic  sulphide  filtered  on  an  alundum  cone,  washed 
with  alcohol,  ether,  again  with  alcohol,  then  carbon  di- 
sulphide,  then  with  alcohol  and  finally  with  ether.  After 
drying  to  constant  weight,  at  100°  C.,  it  was  weighed  as 
arsenic  trisulphide.  By  following  this  method  it  was  not 
difficult  to  get  satisfactory  results. 

Separation  and  Estimation  of  Arsenic  and  Tungsten.— 
Hibbs2  attempted  to  separate  tungsten  and  arsenic  mix- 
tures in  the  form  of  their  sodium  salts,  but  since  the  so- 
dium tungstate  broke  up,  in  part,  into  sodium  chloride 
and  oxides  of  tungsten  he  could  not  calculate  the  amount 
of  arsenic  volatilized  from  the  weight  of  residual  sodium 
chloride.  He  succeeded  in  separating  arsenic  from  pure 
tungsten  trioxide,  however,  and  calculated  the  amount  of 
arsenic  volatilized  by  subtracting  the  known  amount 
of  trioxide  from  the  residual  chloride.  Since  the  amount 
of  tungsten  in  a  sample  will  not,  in  general,  be  known, 
and  since  the  tungsten  will  nearly  always  occur  in  some 
combination  other  than  the  trioxide,  this  method,  of 
course,  has  little  practical  application.  Furthermore, 


1  Zeit.  f.  anal.  Chem.,  1905,  493. 

2  Jour.  Amer.  Chem.  Soc.,  17,  682. 


8 

there  is  always  more  or  less  reduction  to  the  blue  oxides 
when  the  trioxide  is  treated  with  hydrogen  chloride.  , 

Weighed  portions  of  the  arsenate  and  tungstate  were 
exposed  in  a  boat,  to  a  stream  of  hot  hydrogen  chloride. 
The  tungstate  was  immediately  attached,  giving  variously 
colored  products,  depending  upon  the  temperature.  It 
was  found,  however,  that  the  arsenic,  in  the  presence  of 
the  tungstate,  was  completely  expelled  only  with  great 
difficulty.  It  is  remarkable  that  arsenic,  when  combined 
with  sodium  and  oxygen  (Na4As2O7),  should  be  so  easily 
expelled;  and  when  only  mixed  with  a  tungstate  should  be 
so  difficult  to  remove. 

A  large  number  of  experiments  were  made  to  determine 
the  temperature  at  which  a  complete  separation  could  be 
effected.  It  was  found  that  at  too  low  a  temperature  the 
arsenic  could  not  be  completely  expelled:  if  the  tempera- 
ture was  increased  to  300°  C.  the  tungsten  began  to  vola- 
tilize. The  results  of  these  experiments  showed  that  the 
temperature  at  which  it  was  practical  to  remove  the  ar- 
senic was  dangerously  near  the  point  at  which  the  tung- 
sten began  to  volatilize. 

Since  only  a  small  amount  of  the  tungsten  volatilized 
at  300°  C.  (measured  by  a  thermometer  lying  beside  the 
combustion  tube),  it  was  thought  best  to  collect  the  tung- 
sten which  volatilized,  rather  than  to  try  to  regulate  the 
temperature  in  such  a  manner  as  to  completely  prevent  it. 

.  _  /*  _  B  _  B  _  n 


A  tube,  about  fourteen  inches  long,  which  could  be 
pushed  into  the  combustion  tube,  was  constructed  as  shown 
in  Fig.  2.  A  was  the  opening  through  which  the  sample 
was  introduced;  B,  B,  B  were  constrictions,  C  was  the 
exit. 

Procedure:  The  sample  was  placed  in  the  tube  at  E, 
the  tube  was  then  placed  in  the  combustion  tube,  and 


a  current  of  hydrogen  chloride  was  passed  over  it.  The 
temperature  at  E  was  about  300°  C.,  but  at  the  rear  end 
of  the  tube  it  was  kept  much  lower  to  condense  any  tung- 
sten which  might  have  volatilized.  The  substance  which 
volatilized  was  proved  to  be  tungsten,  and  not  an  im- 
purity. 

By  working  in  this  manner  it  was  found  possible  to 
completely  separate  the  arsenic  and  tungsten  in  about 
four  hours. 

After  about  four  hours  the  receiver  was  removed,  the 
combustion  tube  rinsed  out,  and  a  second  receiver  put  in 
place.  After  another  treatment  there  should  be  no  evi- 
dence of  arsenic  in  the  second  receiver. 

The  inner  tube  was  removed,  its  contents  rinsed  into  an 
evaporating  dish  with  dilute  ammonia,  and  evaporated 
to  dryness  on  the  water-bath.  It  was  then  digested  on  the 
water-bath  with  i  :  i  nitric  acid  and  small  quantities 
of  hydrochloric  acid  were  added  from  time  to  time.  When 
all  action  had  ceased  the  watch-glass  cover  was  rinsed  off, 
and  the  liquid  was  evaporated.  The  residue  was  mois- 
tened with  nitric  acid  and  evaporated  several  times  to  re- 
move all  chlorine.  The  residue,  consisting  of  tungsten 
trioxide  and  sodium  nitrate,  was  dissolved  in  sodium  hy- 
droxide, diluted  and  filtered.  A  few  drops  of  methyl- 
orange  were  added,  and  the  solution  was  just  neutralized 
with  nitric  acid.  It  was  then  boiled,  cooled,  and  the  tung- 
sten precipitated  with  mercurous  nitrate.  After  stand- 
ing four  hours  it  was  filtered,  washed  with  two  per  cent 
mercurous  nitrate,  and  ignited  and  weighed  as  tungsten 
trioxide. 

The  method  of  evaporating  with  nitric  acid,  and  then 
filtering  out  the  tungsten  trioxide,  always  gave  low  results. 
The  procedure  described — which  is  really  an  adaptation 
of  Smith  and  Exner's  method  of  getting  pure  tungsten 
trioxide — gave  splendid  results. 

The  following  results  were  obtained: 


10 

Calculated.  Obtained.  Error. 

As2Ss 0.0786  0.0783  — 0.0003 

WO3. 0.0816  0.0817  +0.0001 

AszSs 0.0804  0.0808  +0.0004 

WOg O  .  OQOO  O  .  0898  O  .  OOO2 

As'2S3 0.1470  0.1472  +0.0002 

WO3.. 0.0796     0.0794     — 0.0002 

The  arsenic  was  completely  expelled  from  the  following 
mixtures  as  proved  by  Marsh's  test: 

.    0.0549     0.1082     0.2010     0.1032 
.    0.1297     0.1084     0.1492     0.1248 

It  was  hoped  that  the  procedure  described  above  would 
effect  a  separation  of  arsenic  and  tungsten  when  they 
were  chemically  combined.  Such  was  not  the  case,  how- 
ever. In  order  to  remove  the  last  trace  of  arsenic,  from  an 
arseno-tungstate,  it  was  necessary  to  pass  the  hydrogen 
chloride  for  six  or  seven  days.  This  rendered  the  method 
useless  for  practical  work. 

It  was  found  that  moistening  the  sample  a  few  times 
with  water  exposed  fresh  portions  of  the  unattached  salt 
to  the  gas,  and  made  it  possible  to  completely  remove  the 
arsenic  at  a  much  lower  temperature,  and  in  a  much  shorter 
time.  With  a  tube,  such  as  described  above,  there  was  no 
difficulty  attached  to  this  operation.  Since  there  is  no 
danger  of  loss  by  spattering,  the  water  could  be  evaporated 
in  a  few  minutes. 

The  modified  procedure  was  as  follows:  A  weighed 
portion  of  the  arseno-tungstate  was  brushed  into  the  small 
tube,  and  was  distributed  by  rolling  and  tapping.  It 
was  then  placed  in  the  combustion-tube  and  exposed  to  a 
stream  of  hydrogen  chloride  for  about  an  hour.  The  tem- 
perature, as  measured  by  a  thermometer  lying  beside  the 
combustion  tube,  should  register  about  200°  C.  Since, 
however,  the  temperature  within  the  tube  varies  somewhat 
with  the  construction  of  the  apparatus,  the  proper  tempera- 
ture to  use  was  ascertained  by  turning  the  flames  gradually 
higher  until  the  tungsten  just  began  to  volatilize,  and 


condense  on  the  tube,  over  the  sample;  a  few  degrees 
lower  than  this  was  the  proper  temperature  to  use.  After 
determining  this  point  the  wing-top  burners  were  left 
permanently  adjusted,  the  gas  being  regulated  at  the  gas- 
cock. 

After  about  an  hour  the  apparatus  was  cooled,  the  inner 
tube  removed,  the  sample  moistened  with  water,  the  tube 
replaced,  and  the  gas  passed  for  one-half  hour  longer. 
This  operation  was  repeated  three  times. 

The  receiver  was  then  removed,  and  the  combustion- 
tube  rinsed  into  it.  A  second  receiver  was  then  put  in 
place,  the  sample  again  moistened  and  the  operation  re- 
peated. Should  the  contents  of  the  second  receiver  show 
the  presence  of  arsenic,  when  treated  with  hydrogen  sul- 
phide, it  must  be  added  to  the  first,  and  the  sample  must 
be  further  treated.  The  arsenic  and  tungsten  were  de- 
termined as  described  above. 

The  analysis  is  best  made  on  small  samples. 

The  following  results  were  obtained : 

Sample  of  Percentage  Percentage 

arseno-tungstate.  AszOs.  WOs. 

O. IO28  g.  II .63  71 .OI 

0.1550  11-57  70.83 

0.2858  11-77  70.88 

0:2090  ...  71 . 10 

0.1409  H-93  70.76 

0.2788  H-93  70.91 

The  method  gives  satisfactory  results,  and  does  not  re- 
quire a  longer  time  than  many  other  analytical  procedures 
which  have  been  generally  adopted. 

SEPARATION    OF   ANTIMONY    AND   TUNGSTEN. 

Procedure:  Weighed  portions  of  potassium  anti- 
monio-tungstate  were  introduced  into  the  tube,  and  sub- 
jected to  the  action  of  hydrogen  chloride  exactly  as  de- 
scribed in  the  separation  of  arsenic  and  tungsten.  It 
was  found  advisable  to  pass  the  hydrogen  chloride,  in  the 
cold,  for  about  one-half  hour  before  lighting  the  burners. 


12 

The  alternate  treatment  with  hydrogen  chloride  and  water 
should  be  continued  until  a  film  of  antimony  oxychloride 
no  longer  forms  in  the  cool  portion  of  the  combustion 
tube.  The  deposit  of  oxychloride  could  be  driven  into  the 
receiver  by  "brushing"  the  combustion  tube  with  the  flame 
of  a  Bunsen  burner. 

When  the  antimony  oxychloride  no  longer  condensed 
in  the  cool  portions  of  the  tube  the  apparatus  was  rinsed, 
the  receiver  changed,  and  another  put  "in  place.  The 
sample  was  moistened  with  water,  the  water  evaporated, 
and  again  treated  with  hydrogen  chloride.  The  second 
receiver  should  show,  at  most,  only  a  slight  yellow  tinge 
with  hydrogen  sulphide. 

The  tungsten  was  determined  as  described  under  ar- 
senic. 

The  antimony  was  precipitated  with  hydrogen  sulphide, 
filtered  through  an  alundum  crucible,  ignited  in  a  current 
of  carbon  dioxide  to  constant  weight,1  and  weighed  as 
antimony  trisulphide.2 

The  methods  employed  by  Gibbs  for  the  analysis  of 
these  complexes  were  described  by  him  as  very  unsatisfac- 
tory. The  results  obtained  varied  several  per  cent,  and 
for  that  reason  it  was  not  possible  to  check  the  hydrogen 
chloride  method  by  another  analytical  method.  Careful 
tests  were  made  to  prove  that  the  antimony  was  all  out 
of  the  residue;  and  care  was  used  to  prevent  any  loss  dur- 
ing the  process.  The  following  concordant  results  proved 
the  accuracy  of  ^he  method: 

Samples. 
O. 1462 
0.0799 
o. 1090 
o. 1811 
0.1582 
o . 3040 


Percentage  Sb2Os. 

Percentage  WOa. 

66.87 

16.07 

66.84 

16.02 

66.81 

15.96 

15.90 

66.85 

15-86 

67.01 

16.05 

1  Treadwell  and  Hall:     Text-book,  p.  187. 

2  The  carbon  dioxide  must  be  free  from  hydrogen  chloride. 


13 

SEPARATION    OF   VANADIUM    AND   TUNGSTEN. 

On  passing  hydrogen  chloride  over  vanadio-tungstic 
acid  the  vanadium  came  off  as  a  heavy  red  vapor  which 
condensed  to  a  reddish  brown  liquid.  The  residue  was 
soon  reduced,  however,  to  a  brownish  mass  which  was  no 
longer  attacked.  By  introducing  chlorine  along  with  the 
hydrogen  chloride  the  vanadium  was  more  completely 
expelled.1 

Attempts  were  made  to  separate  the  tungsten  and 
vanadium,  in  a  tube,  as  in  the  case  of  arsenic  and  antimony. 
After  moistening,  however,  the  sample  crept  so  much  that 
the  results  were  always  low  for  tungsten.  A  distilling 
bulb  was  substituted  and  worked  somewhat  better.  The 
vanadium  condensed  in  the  neck  of  the  bulb,  however, 
and  was  sometimes  drawn  into  the  ground  glass  joint. 
For  this  reason  the  piece  was  discarded.  After  experi- 
menting with  several  devices  the  piece  shown  in  Fig.  3 
was  found  to  be  very  satisfactory. 

The  tube  was  made  in  one  piece  as  shown.  It  consisted 
of  one-inch  soft  glass  tubing  A,  to  which  was  sealed  a  one- 
half  inch  exit  tube,  B.  To  the  exit  tube  a  calcium  chloride 
tube  was  sealed;  this  prevented  the  water  from  being 
drawn  back  into  the  hot  tube.  The  receiver  was  a  large 
test-tube.  The  piece  was  surrounded  by  a  tin  box,  C, 
to  act  as  an  oven.  It  was  provided  with  a  thermometer. 
By  sealing  on  D,  a  small  separatory  funnel,  the  sample 
could  be  moistened  without  "breaking"  the  ground-glass 
joint  E.  The  dimensions  should  be  about  as  given. 
Such  a  piece  is  easily  cleaned,  and  the  vanadium  will  not 
diffuse  back  to  the  joint.  After  it  is  once  started  it  re- 
quires no  attention. 

Chlorine  was  generated  by  dropping  hydrochloric  acid 
upon  potassium  permanganate.  Hydrogen  chloride  was 
generated  in  the  usual  manner.  The  mixed  gases  were 
passed  through  two  wash  bottles  containing  sulphuric  acid. 


1  McAdam:     Jour.  Amer.  Chem.  Soc.,  32. 


14 

Procedure:  Weighed  portioijs  of  the  vanadio-tungstate 
were  introduced  into  the  tube  by  means  of  a  piece  of  glazed 
paper.  On  passing  hydrogen  chloride,  containing  a  small 
amount  of  chlorine,  the  sample  was  attached  with  the  forma- 
tion of  a  reddish  brown  volatile  liquid.  After  a  time  a 


gentle  heat  was  applied  to  the  oven,  and  the  temperature 
was  gradually  increased  until  it  reached  200°  C. 

Since  too  much  heat  converts  this  body  into  a  green, 
non-volatile  solid,  care  should  be  taken  not  to  heat  it  too 
strongly.  This  green  residue  is  soluble  in  water,  and  on 


15 

evaporation  it  again  becomes  volatile  in  hydrogen  chloride. 
When  the  vanadium  condenses  in  the  neck  of  the  tube  it 
should  be  allowed  to  distill  off  slowly  in  the  stream  of 
hot  hydrogen  chloride.  The  gas  was  passed  rapidly 
enough  to  prevent  the  vanadium  from  diffusing  back 
to  the  ground  joint. 

The  receiver  contained  about  one  hundred  and  twenty- 
five  cc.  of  water,  and  the  exit  tube  dipped  under  the  water 
only  a  short  distance. 

After  about  an  hour  the  piece  was  cooled,  and  five  cc. 
of  10%  sodium  hydroxide  were  added.1  After  evaporating 
in  a  stream  of  the  gases  it  was  again  heated,  for  one-half 
hour,  at  200°  C.  After  this  it  was  alternately  moistened 
with  water  and  treated  with  the  gas  mixture  until  the  red 
vanadium  compound  no  longer  appeared  in  the  cool  por- 
tion of  the  exit  tube.  The  rear  end  of  the  tube  was  then 
rinsed  out,  a  second  receiver  put  in  place,  and  the  opera- 
tion repeated. 

The  appearance  of  this  red  film  proved  to  be  a  very 
delicate  test  for  vanadium.  When  it  no  longer  appeared 
the  vanadium  was  always  found  to  be  completely  expelled. 
The  precaution  of  an  extra  treatment  was  usually  observed, 
however. 

The  tungsten  was  removed  from  the  tube  with  am- 
monium hydroxide,  and  was  then  determined  as  described 
under  arsenic. 

Various  methods  for  determining  vanadium  were  stud- 
ied, and  it  was  finally  decided  that  the  volumetric  method 
using  potassium  permanganate,  was  best  suited  to  the 
conditions  presented  by  the  hydrogen  chloride  method. 
Experiments  were  made  to  prove  that  there  was  no  loss 
on  evaporating  a  strong  hydrochloric  acid  solution  of 
vanadium.  Such  a  solution  was  evaporated,  in  a  retort, 


1  This  was  necessary  since  the  vanadio-tungstic  acid  contained 
no  sodium  or  potassium,  and,  for  that  reason,  a  soluble  residue  re- 
sulted on  treating  with  hydrogen  chloride. 


i6 

the  distillate  was  collected,  and  failed  to  show  the  faintest 
color  with  hydrogen  peroxide. 

The  procedure  was  as  follows:  The  receiver  contents, 
and  exit-tube,  were  rinsed  into  an  evaporating  dish,  five 
cc.  of  concentrated  sulphuric  acid  were  added,  and  the 
solution  evaporated,  as  far  as  possible,  on  the  water-bath. 
It  was  then  heated,  over  a  low  flame,  until  white  fumes  of 
sulphuric  acid  came  off.  The  contents  of  the  dish  were  next 
rinsed  into  an  Erlenmeyer  flask,  diluted  to  two  hundred 
cc.,  heated  to  boiling,  and  a  stream  of  sulphur  dioxide 
passed  in  to  completely  reduce  the  vanadium  to  the  vanadyl 
salt.1  The  boiling  was  continued  and  a  stream  of  carbon 
dioxide  was  passed  to  remove  the  excess  of  sulphur  dioxide. 
When  all  the  sulphur  dioxide  was  expelled  the  solution 
was  titrated,  while  still  hot,  with  potassium  permanga- 
nate. The  permanganate  was  standardized,  with  pure 
vanadium  pentoxide,  which  had  been  reduced  in  the  same 
manner. 

The  following  results  were  obtained: 

Vanadio-tungstic  acid.        Percentage  VaOs.  Percentage  WOs. 

0.2204  ...  65.47 

0.3396  65.31 

0.3227  16. 17 

0.3022  I5-92  65.35 

0.3127  15.90 

0.2460  15-95  65.20 

0.2487  15.95  65.38 

0.1848  16.09  65.39 

This  latter  method  is  so  satisfactory  that  it  is  recom- 
mended in  preference  to  the  others.  The  temperature  is 
easily  regulated;  the  piece  can  be  cooled  quickly  by  re- 
moving the  oven ;  the  danger  of  loss  from  creeping  is  slight ; 
and  the  volatile  constituent  is  more  quickly  removed. 


1  Repeated   evaporation  with   hydrochloric   acid  will  also   effect 
this  reduction. 


'7 

CONCLUSIONS. 

1.  Methods   are   given   for   the   separation   of   arsenic, 
antimony  and  vanadium  from  tungsten,  which,  it  is  be- 
lieved,   are   more    satisfactory   than   those   previously   de- 
scribed. 

2.  Procedures   are    described    which    are    suitable    for 
estimating  the  separated  constituents. 

3.  A  piece  of  apparatus  has  been  devised  which  sim- 
plifies the  analytical  procedures. 


II.    ON  THE  COMPLEX  BISMUTHICO-TUNGSTATES 

In  a  contribution  by  Balke  and  Smith1  the  ammonium, 
potassium  and  strontium  salts  of  a  bismuthico-tungstic 
acid,  having  the  composition  3M2/O.2Bi2O3.iiWO3.A:H2O 
were  described.  In  this  paper  the  corresponding  mer- 
curous  salt  is  described,  and  some  further  observations  are 
recorded. 

The  ammonium  bismuthico-tungstate  was  prepared  by 
adding  small  portions  of  bismuth  hydroxide,  as  it  dissolved, 
to  a  boiling  solution  of  ammonium  para-tungstate.  After 
boiling  for  two  days  it  was  filtered,  evaporated  to  dryness, 
and  extracted  with  boiling  water.  On  cooling  an  oil 
separated  from  the  solution  having  all  the  properties  of 
the  ammonium  bismuthico-tungstate  described  in  the 
paper  cited  above.  It  is  worthy  of  note  that  this  substance 
had  a  distinct  oily,  organic  odor  when  warm.  The  am- 
monium salt  was  dissolved  in  water  and  on  adding  a  con- 
centrated solution  of  potassium  bromide  the  less  soluble 
potassium  salt  separated. 

A  solution  of  the  potassium  salt  was  treated  with  a  solu- 
tion of  mercurous  nitrate.  A  light  yellow  precipitate 
separated,  and,  after  standing  several  hours,  with  occa- 
sional shaking,  it  was  filtered  and  dried.  The  dry  pre- 


1  Jour.  Amer.  Chem.  Soc.,  25,  12. 


i8 

cipitate  was  a  yellow  insoluble  powder.  On  gently  igniting 
it  the  color  deepened  to  a  rich  brown;  but  on  stronger 
heating  it  began  to  decompose  becoming  lemon  yellow  in 
color. 

Analysis:  The  mercury  was  determined  by  covering 
the  salt  with  water  and  adding  dilute  hydrochloric  acid 
in  slight  excess.  After  standing  over  night  it  was  warmed 
on  the  water-bath,  filtered  into  a  Gooch  crucible,  washed 
with  two  per  cent  hydrochloric  acid,  dried  at  100°  C.  and 
was  then  weighed.  The  residue  always  contained  slight 
amounts  of  the  undecomposed  bismuthico-tungstate.  To 
correct  for  this  the  mercurous  chloride  was  expelled  by 
heating  the  crucible,  and  the  weight  of  the  residue  was  sub- 
tracted from  the  weight  first  obtained.  The  weight  of 
this  residue  was  probably  low  due  to  the  volatilization  of 
some  of  the  bismuth.  (See  below.) 

The  tungsten  and  bismuth  were  determined  together 
by  gently  igniting  the  mercury  salt  in  a  porcelain  crucible. 
The  mercury  and  water  were  volatilized  leaving  the  oxides 
of  bismuth  and  tungsten.  It  is  best  to  place  the  crucible 
in  a  larger  crucible,  and  heat  the  outer  crucible  with  the 
flame  of  a  Bunsen  burner.  If  the  temperature  be  too  high 
some  of  the  bismuth  will  volatilize,  and  there  may  be  re- 
duction to  the  blue  oxides  of  tungsten.  Better  results 
were  obtained  by  igniting  in  a  weighed  amount  of  sodium 
tungstate  as  recommended  by  Gibbs.  The  bismuth 
and  tungsten  can  be  separated  in  the  residue  by  boiling 
with  aqua  regia.  The  crucible  contents  were  covered 
with  aqua  regia  and  evaporated  to  dryness  on  the  water- 
bath  ;  it  was  then  treated  with  i  :  i  nitric  acid,  evaporated, 
again  taken  up  with  nitric  acid,  and  filtered.  The  filtrate 
was  again  evaporated,  taken  up,  and  filtered  to  recover 
some  tungsten  which  still  remained  in  solution.  The 
tungsten  trioxide  was  weighed  as  such:  the  bismuth  was 
precipitated  from  the  filtrate  as  the  basic  carbonate  and 
was  ignited  to  the  oxide  and  weighed. 


f  '9 

Found.  Theory. 

Hg,O  +  H20 30.08%  30.36% 

W03  +  Bi203 69.93  69.64 

Hg20 26.65  24.96 

H2O  (by  difference) 3 . 7 1  5  . 40 

WO3 50.41  51-04 

Bi2O3 17.36  18.60 

The  above  results  indicate  that  the  ratio  3Hg2O.2Bi2O3.- 
iiWO3.i5H2O  maintains  for  the  mercurous  salt.  To  be 
sure  the  mercury  is  much  too  high,  and  since  the  water 
was  obtained  by  difference,  it  was,  of  course,  too  low. 
In  the  analysis  the  precipitate  obtained  was  not  pure  mer- 
curous chloride,  but  a  mixture  of  mercurous  chloride  and 
some  of  the  complex  which  had  not  completely  transposed. 
On  drying  the  mercurous  chloride  and  this  complex  were 
weighed  together.  On  ignition  to  expel  the  mercurous 
chloride  some  bismuth  was  also  volatilized  as  the  chloride, 
and  any  water  which  might  have  been  retained  with  the 
complex  would  also  be  expelled.  This  all  tends  to  make 
the  mercury  high.  Considering  this  expected  error, 
together  with  the  good  agreement  of  the  Hg2O  +  H2O 
and  the  WO3  +  Bi2O3,  it  is  fair  to  conclude  that  the  ratio 
is  the  same  as  that  for  the  ammonium,  potassium  and, 
strontium  salts. 

The  body  was  well  defined  and  thoroughly  stable. 

Having  obtained  the  mercury  salt  the  intention  was  to 
isolate  the  free  acid  and  endeavor  to  obtain  a  non-ionizing 
solvent  for  it.  If  such  a  solvent  could  be  obtained  it  would 
be  possible  to  learn  its  molecular  magnitude. 

Hydrochloric  acid  was  added  in  slight  excess,  and, 
after  filtering  from  mercurous  chloride,  the  solution  was 
evaporated  to  dryness.  The  resulting  body  was  not 
homogeneous.  It  was  thought  that  the  bismuthico- 
tungstic  acid  might  be  more  stable  in  neutral  solution; 
accordingly  the  mercury  salt  was  covered  with  water, 
and  such  an  amount  of  hydrochloric  acid  was  added  as 
would  leave  a  part  of  the  salt  undecomposed.  After  di- 
gesting several  hours  in  the  cold,  with  occasional  shaking, 


20 

it  was  filtered.  The  water  solution  was  evaporated,  under 
reduced  pressure,  and  at  a  low  temperature.  When  the 
water  was  nearly  all  removed  a  greenish  oily  body  separated. 
The  last  traces  of  water  were  allowed  to  evaporate  at  ordi- 
nary temperature. 

After  the  water  had  evaporated  large  quantities  of  hy- 
drogen chloride  commenced  to  come  off.  The  sample  was 
placed  in  a  desiccator,  over  sodium  hydroxide,  until  the 
hydrogen  chloride  was  completely  removed.  The  body 
fell  to  a  greenish  yellow  solid. 

This  behavior  was  remarkable.  It  was  expected  that  the 
reaction  would  be 

3Hg2O.2Bi2O3.iiWO3  +  6HC1   = 

3H2O.2Bi2O3.iiWO3  +  6HgCl. 

When  it  was  observed  to  contain  hydrogen  chloride  it 
was  first  thought  that  the  hydrogen  chloride  had  added 
on  in  place  of  water  of  crystallization  giving  3H2O.2Bi2O3.- 
nWO3.#HCl.  Later  behavior  seemed  to  indicate  that 
the  hydrogen  chloride  had  replaced  the  Hg2O,  and  that 
it  possessed  some  such  composition  as  6HC1.2Bi2O3.- 
nWO3. 

The  compound,  after  losing  its  hydrogen  chloride, 
was  no  longer  soluble  in  water,  or  even  acids.  In  an  effort 
to  find  a  solvent  for  it  the  following  reagents  were  used: 
Alcohol,  ether,  acetone,  pyridine,  quinoline,  nitro-benzine, 
benzene,  toluene,  aniline,  acetic  acid,  carbon  tetrachloride 
and  carbon  disulphide,  none  of  which  effected  a  solution. 
If  the  hydrogen  chloride  had  merely  added  on,  like  water 
of  crystallization,  it  would  have  been  expected  to  redis- 
solve  in  this  acid. 

The  insolubility  of  this  body  rendered  it  useless  as  a  ma- 
terial from  which  to  determine  the  molecular  magnitude. 

It  was  noticed  that  the  mercurous  salt  gave  a  colloidal 
suspension  in  acetone,  and  on  adding  hydrochloric  acid, 
it  entered  into  solution  with  the  separation  of  mercurous 
chloride  and  some  free  mercury.  It  was  hoped  that  the 


21 

free  acid  could  be  obtained  from  this  solution,  but  on  evap- 
orating a  dark  green  powder  separated,  which  was  not  re- 
dissolved  by  acetone  or  acids. 

On  adding  barium  chloride  to  a  solution  of  the  ammonium 
salt  a  white  viscous  oil  separated.  This  dried  to  a  solid 
glass  resembling  the  strontium  salt. 

CONCLUSIONS. 

1.  The    mercurous    salt     of     bismuthico-tungstic    acid 
corresponding   to   ratios   already   obtained,  was  prepared, 
and  was  found  to  be  a  stable  body. 

2.  Attempts   to   prepare   the   free   bismuthico-tungstic 
acid  were  unsuccessful,  and  would  lead  to  the  conclusion 
that  the  acid  3H2O.2Bi2O3.i  iWO3,  like  H2CO3  and  many 
other  acids,  is  so  unstable  as  to  exist  only  in  the  form  of  its 
salts. 

3.  When  liberated  from  its  mercury  salt,  with  hydro- 
chloric  acid,    the   complex   unites   with   the   hydrochloric 
acid  to  form  a  compound  which  is  only  stable  in  solution. 


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